Invalid Pointer access when new Curreny Pair is initialized

[hoermann-p]

I setup a quick Test-EA in order to get used to the library.
However I got an invalid pointer access message when I drag/drop a different currency pair onto the chart where the Test-EA is running.

Is there anything I am missing?
I placed the config and .mq4 file into the right directories.

Following is the code:

//+------------------------------------------------------------------+
//| ProjectName |
//| Copyright 2018, CompanyName |
//| http://www.companyname.net |
//+------------------------------------------------------------------+
#define _version "1.03"
#property copyright "Copyright © ";
#property link "";
#property version _version;
#property strict

#import "stdlib.ex4"
string ErrorDescription(int);
#import

#include "........\Libraries\log4mql.mqh"; // Include loging module

//+------------------------------------------------------------------+
//+------------------------------------------------------------------+

CLog4mql* logger = CLog4mql::getInstance();

int OnInit()
{
// Validate Inputs
// logger.setConfLogFile( StringConcatenate(Default_Folder,"/", Default_FileName ) );
logger.info(FILE, LINE, "Start Init with Input check...");
return 0;
}

void OnDeinit(const int reason){
logger.release();
}

void OnTick()
{
}